1. Field of the Invention
The invention relates to the field of veterinary medicine and more particularly to a device and method for detecting pancreatic lipase. The device and method may be used in the diagnosis and management of pancreatitis in animals.
2. Description of Related Art
Lipases are glycoprotein triglyceride hydrolases which catalyze the cleavage of triglycerides to diglycerides with subsequent formation of monoglycerides and fatty acids. Excess serum lipase is a symptom of pancreatitis, a disease of the pancreas characterized, in part, by excess lipase, protease and amylase production. Excess lipase production may, in turn, lead to numerous symptoms ranging from mild discomfort or death, depending, in part, on the severity of the disease and the extent of lipase overproduction.
Pancreatic lipases have for many years been important clinical chemistry parameters for the differential diagnosis of diseases of the pancreas. Numerous methods including enzymatic assays have been described for detecting lipase. Generally, however, these assays have had poor correlation between lipase activity determined in serum and the extent of damage to the pancreas. In particular, enzymatic assays for lipase have been found to be not specific enough to distinguish lipase activity originating from organs other than the pancreas.
Recently, a colorimetric test specific for pancreatic lipase in humans, based on the cleavage of a chromogenic lipase substrate 1,2-O-dilauryl-rac-glycero-3-glutaric acid-(6-methyl-rsorufin) ester (“DGGR”), has been described. For example, Lipase Colorimetric Assay reagents are available from Roche Diagnostics, GmbH (Mannheim Germany). This assay is sold as a kit with two separate reagents. The first reagent includes a buffer, and the DGGR substrate emulsified with a bile acid (taurodeoxy-cholate). The second reagent includes a buffer, a colipase and a cholate. The pancreatic lipase activity is determined specifically by the combination of the bile acid and the colipase used in the assay. Virtually no lipase activity is detected in the absence of the colipase. Colipase only activates pancreatic lipase, but not other lipolytic enzymes found in serum. The high amount of cholate ensures that the esterases present in the serum do not react with the chromogenic substrate due to the highly negative surface charge.
The DGGR substrate is cleaved by the catalytic action of the alkaline lipase solution to form 1,2-O-dilauryl- rac-glycerol and an unstable intermediate, glutaric acid-(6-methylresorufin) ester. This decomposes spontaneously in alkaline solution to form glutaric acid and methylresorufin. The color intensity of the red dye formed is directly proportional to the lipase activity and can be determined photometrically.
Other commercially available lipase assays include the Lipase Color Liquid assay from Sentinel Diagnostics, Milan, Italy, and the Coloripase Coloriometic Assay from Nuclin Diagnostics, Inc., Northbrook Ill.
The window for measurement of serum lipase is 14 days after an onset of acute pancreatitis, the peak of lipase activity reached within 24 hours and decreasing after 8 to 14 days. In animals, symptoms of pancreatitis are generally non-specific, with vomiting being the most common symptom presented to the clinician. This symptom, however, is indicative of many other diseases. Currently, animal testing for pancreatic lipase is performed at a reference laboratory remote from the clinic, which delays the diagnosis and, therefore, the treatment of the disease. Moreover, current calorimetric methods require automated or semi-automated diagnostic equipment to efficiently render a result. Rapid and specific clinic-based methods for pancreatic-specific lipase will allow rapid diagnosis and treatment of the patient.